spring和mybatis的使用心的
作者:互联网
1.spring和mybatis的整合
a)数据源的配置(通过properties引入数据)
b)spring和mybatis的扫包(spring需要扫包,mybatis也需要扫包)
c)全局懒加载的配置
d)事务管理者的配置
e)注解驱动的配置
f)dao层映射配置(保证映射名称一致,切勿忘记大小写问题)
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.2.xsd">
<!--开启事务注解驱动-->
<tx:annotation-driven />
<!--加载配置文件-->
<context:property-placeholder location="classpath:db.properties"/>
<!--配置数据源-->
<bean id="datasource" class="com.alibaba.druid.pool.DruidDataSource">
<property name="username" value="${user}"/>
<property name="url" value="${url}"/>
<property name="password" value="${password}"/>
<property name="driverClassName" value="${driver}"/>
</bean>
<!--加载mybatis的核心配置文件-->
<bean id="sqlSessionFactoryBean" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="datasource"/>
<property name="configLocation" value="classpath:SqlMapConfig.xml"/>
</bean>
<!--配置事务管理者-->
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="datasource"></property>
</bean>
<!--扫描dao-->
<bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.brant.dao"/>
</bean>
<!--扫描-->
<context:component-scan base-package="com.brant"></context:component-scan>
</beans>
2.使用mybatis查询返回值为空
a)当时mybatis查询数据时,存在返回值为空的情况
b)因此,可以在controller和dao层中做以下处理,将返回值封装成一个Map集合再进行返回
@Override
public Map findUserById(int user_id) {
Map userMap = new HashMap();
UserInfo user = userDao.findUserById(user_id);
if(user != null){
userMap.put("user",user);
return userMap;
}
return userMap;
}
3.一层嵌套延迟加载和两层嵌套延迟加载https://www.cnblogs.com/kenhome/p/7764398.html
a)开启全局延迟加载
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--
根标签是configuration
-->
<configuration>
<!--全局懒加载 -->
<settings>
<setting name="lazyLoadingEnabled" value="true"/>
<setting name="aggressiveLazyLoading" value="false"/>
</settings>
<!--批量定义别名-->
<typeAliases>
<package name="com.wangshidai.eshopFront.pojo"/>
<package name="com.wangshidai.eshopFront.entity"/>
</typeAliases>
</configuration>
b)一层嵌套延迟加载
<mapper namespace="com.brant.dao.BookDao">
<resultMap id="findBookOneTypeMap" type="RootTypeInfo" autoMapping="true">
<id column="type_id" property="type_id" />
<collection property="oneTypeList" select="com.brant.dao.BookDao.findBookOneType" autoMapping="true" column="type_id">
</collection>
</resultMap>
<select id="findBookType" resultMap="findBookOneTypeMap">
select * from tb_type where parent_id = 0
</select>
<select id="findBookOneType" parameterType="String" resultType="RootTypeInfo">
select * from tb_type where parent_id = #{type_id}
</select>
</mapper>
. c)两层嵌套延迟加载(省份,城市,地区三级联动)
<mapper namespace="com.wangshidai.eshopFront.dao.AddressDao">
<!--省份连接城市-->
<resultMap id="cityListMap" type="Province" autoMapping="true">
<id column="provinceid" property="provinceid" />
<collection property="citys" autoMapping="true" select="com.wangshidai.eshopFront.dao.AddressDao.findCity" column="provinceid" />
</resultMap>
<select id="findProvince" ofType="Province" resultMap="cityListMap">
select * from provinces
</select>
<!--城市连接地区-->
<resultMap id="areaListMap" type="City" autoMapping="true">
<id column="cityid" property="cityid" />
<collection property="areas" autoMapping="true" select="com.wangshidai.eshopFront.dao.AddressDao.findArea" column="cityid"/>
</resultMap>
<select id="findCity" parameterType="String" ofType="City" resultMap="areaListMap">
select * from cities where provinceid = #{provinceid}
</select>
<select id="findArea" parameterType="String" resultType="Area">
select * from areas where cityid = #{cityid}
</select>
</mapper>
4.jackson解析数据时,出现异常
Could not write JSON: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS);
. 1)解决:在jackson解析的Bean类加上@JsonIgnoreProperties(value = “handler”) 注解,并实现序列化
5.mybatis获取插入值自增长ID
<insert id="insert" parameterType="Spares"
useGeneratedKeys="true" keyProperty="id">
insert into system(name) values(#{name})
</insert>
<!--
@Override
public int register(UserInfo userInfo) {
int count = regDao.register(userInfo);
return userInfo.getUser_id() ;
}
//获取到的ID就是插入的ID,通过形参中userDao对象获取
-->
. a)注意:keyProperty和java对象的属性名称保持一致,传递的参数必须是Bean
标签:userMap,spring,user,使用,mybatis,id,select,加载 来源: https://blog.csdn.net/brantykl/article/details/122838473